Causes of Coastal Flooding: CFAS
Learn about how climate change and sea level rise is driving increased coastal flooding
Coastal flooding in Surrey is impacted by the sea and by rain as shown below:
As with many coastal floodplains around the world, the two principal causes of increased coastal flooding in Surrey’s coastal floodplain are climate change related to sea level rise and increased rain.
Learn more about sea level rise and increased rain
- Sea Level Rise
- Increased Rainfall
Sea Level Rise
Global sea level is rising. This is a result of increasing temperatures throughout the world that are melting glaciers and polar ice caps, and that are also increasing the average temperature of ocean waters causing them to expand. In BC, ocean levels are anticipated to rise by a least 1 metre in 80 years, and by at least 2 metres by 2200.
The global climate is also changing. In general, this means that we can expect more extreme weather conditions. In Surrey, winters are expected to have fewer wet days, but on the wet days the rainfall amounts will be much greater than in the past. This will result in increased flooding, as more runoff flows into the Nicomekl, Serpentine and Little Campbell Rivers during these storm events. The frequency and intensity or storm events with heavy precipitation in a short amount of time are also expected to increase.
In the Mud Bay and Boundary Bay Floodplains, sea level rise is putting pressure on the existing protection systems. Today, Surrey’s dykes are below the height required for anticipated future sea level rise (1 metre by 2100). In places, some dykes have come close to overtopping when high tides and storm surges work together with wind to push the ocean water higher up on the dyke face.
Dykes also face the issue of sliding and erosion due to increased periods of saturation and increased wave impact, as well as overtopping due to increased wave and wind action during coastal storm surges.
Sea dams and flood boxes will become less effective as sea levels rise
In turn, the water levels in rivers, ditches and adjacent lowlying areas will have the potential during storms to flood more frequently and severely.
Sea level rise also combines with and builds on other coastal flood hazards. This includes higher rates of salt water intrusion where sea water moves through the ground into and behind coastal dykes. This can impact infrastructure in the ground (salt water is corrosive) and soil health.